Xinha has many configuration options. These are explained on the Xinha website in its configuration documentation.

A common reason for modifying the default Xinha configuration is to disable the behaviour that makes all links relative to the page the link is on (that is, it removes the domain name from the url).

If you want to configure your Xinha editor you should modify the settings in the configuration file in your site:
/config/config.js

You will need FTP access to be able to upload this file.